title: High genetic compatibility and increased pathogenicity of reassortants derived from avian H9N2 and pandemic H1N1/2009 influenza viruses.
abstract: H9N2 influenza viruses have been circulating worldwide in multiple avian species and repeatedly infecting mammals, including pigs and humans, posing a significant threat to public health. The coexistence of H9N2 and pandemic influenza H1N1/2009 viruses in pigs and humans provides an opportunity for these viruses to reassort. To evaluate the potential public risk of the reassortant viruses derived from these viruses, we used reverse genetics to generate 127 H9 reassortants derived from an avian H9N2 and a pandemic H1N1 virus, and evaluated their compatibility, replication ability, and virulence in mice. These hybrid viruses showed high genetic compatibility and more than half replicated to a high titer in vitro. In vivo studies of 73 of 127 reassortants revealed that all viruses were able to infect mice without prior adaptation and 8 reassortants exhibited higher pathogenicity than both parental viruses. All reassortants with higher virulence than parental viruses contained the PA gene from the 2009 pandemic virus, revealing the important role of the PA gene from the H1N1/2009 virus in generating a reassortant virus with high public health risk. Analyses of the polymerase activity of the 16 ribonucleoprotein combinations in vitro suggested that the PA of H1N1/2009 origin also enhanced polymerase activity. Our results indicate that some avian H9-pandemic reassortants could emerge with a potentially higher threat for humans and also highlight the importance of monitoring the H9-pandemic reassortant viruses that may arise, especially those that possess the PA gene of H1N1/2009 origin.
authors.affiliation: Key Laboratory of Zoonosis of Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China.
authors.forename: Yipeng
authors.initials: Y
authors.lastname: Sun
authors.forename: Kun
authors.initials: K
authors.lastname: Qin
authors.forename: Jingjing
authors.initials: J
authors.lastname: Wang
authors.forename: Juan
authors.initials: J
authors.lastname: Pu
authors.forename: Qingdong
authors.initials: Q
authors.lastname: Tang
authors.forename: Yanxin
authors.initials: Y
authors.lastname: Hu
authors.forename: Yuhai
authors.initials: Y
authors.lastname: Bi
authors.forename: Xueli
authors.initials: X
authors.lastname: Zhao
authors.forename: Hanchun
authors.initials: H
authors.lastname: Yang
authors.forename: Yuelong
authors.initials: Y
authors.lastname: Shu
authors.forename: Jinhua
authors.initials: J
authors.lastname: Liu
mesh_terms: D000818:Animals; D005814:Genes, Viral; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology; D053127:Influenza A Virus, H9N2 Subtype / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology; D051379:Mice; D008969:Molecular Sequence Data; D016865:Reassortant Viruses / Q000472:pathogenicity*; D014779:Virus Replication